Meningitis, bacterial

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Meningitis, bacterial

BASICS

DESCRIPTION:

Inflammation in response to bacterial infection of the pia-arachnoid and its fluid and the fluid of the ventricles. Meningitis is always cerebrospinal.
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System(s) affected: Nervous
Genetics: Navajo Indian and American Eskimo may have genetic or acquired vulnerability to invasive disease
Incidence/Prevalence in USA: 3-10 cases per 100,000 population
Predominant age: Neonates, infants and geriatric aged
Predominant sex: Male = Female

SIGNS AND SYMPTOMS:

  •Antecedent URI
  •Fever
  •Headache
  •Meningismus
  •Signs of cerebral dysfunction
  •Vomiting
  •Photophobia
  •Seizures
  •Nausea
  •Rigors
  •Profuse sweats
  •Weakness
  •Altered mental status
  •Focal neurologic deficits
  •Elderly have subtle findings commonly including confusion
  •Meningococcemia has rash - macular and erythematous at first, then petechial or purpuric

CAUSES:

  •Neonates: Group B or D Streptococcus, Escherichia coli, Listeria monocytogenes and non-group B Streptococcus
  •Infants/children: H. influenzae (48%), Streptococcus pneumoniae (13%), and Neisseria meningitidis
  •Adults: Streptococcus pneumoniae (30-50%), Haemophilus influenzae (1-3%), Neisseria meningitidis (10-35%), gram-negative bacilli (1-10%), Staphylococci (5-15%), Streptococci (5%) and Listeria species(5%)

RISK FACTORS:

  •Immunocompromised host
  •Alcoholism
  •Neurosurgical procedure or head injury
  •Abdominal surgery for gram-negative

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS:

  •Bacteremia
  •Sepsis
  •Brain abscess
  •Seizures
  •Other nonbacterial meningitides

LABORATORY:

  •Turbid CSF
  •Neonates
      •> 10 WBC's in CSF
      •CSF: blood glucose ratio < 0.6
      •CSF protein >150 mg/dL (> 1500 mg/L)
  •Infants/children
      •> 5 WBC's in CSF
      •CSF: blood glucose ratio < 0.6
      •CSF protein > 50 mg/dL (> 500 mg/L)
  •Adults
      •1000-100,000 WBC's in CSF (average 5000-20,000)
      •CSF: blood glucose ratio < 0.4
      •CSF protein > 45 mg/dL (> 450 mg/L) (usually 150-400 mg/dL [1500-4000 mg/L])
      •Suspect ruptured brain abscess when WBC count is unusually high (±100,000)
  •In all age groups:
      •CSF opening pressure > 180 mm H2O (1.77 kPa)
      •CSF Gram stain + in 75% of untreated patients
      •CSF culture + 70-80% of the time
      •Blood culture + 40-60% of the time
      •CSF bacterial antigen test (sensitivity varies)

Drugs that may alter lab results: N/A
Disorders that may alter lab results: N/A

PATHOLOGICAL FINDINGS:

N/A

SPECIAL TESTS:

N/A

IMAGING:

  •CT scan of head if concern for increased intracranial pressure (ICP)
  •Chest x-ray may reveal silent area of pneumonitis or abscess
  •Sinus/skull x-rays may reveal cranial osteomyelitis, paranasal sinusitis or skull fracture
  •Later in course, head CT scan, if hydrocephalus, brain abscess, subdural effusions or subdural empyema are considered

DIAGNOSTIC PROCEDURES:

Lumbar puncture

TREATMENT

APPROPRIATE HEALTH CARE:

Inpatient often with ICU. If diagnosis is suspected, lumbar puncture should be done in office with antimicrobial therapy begun before transfer to hospital.

GENERAL MEASURES:

  •Appropriate antibiotic therapy
  •Vigorous supportive care with constant nursing to ensure prompt recognition of seizures and prevention of aspiration
  •Therapy for any coexisting conditions
  •Measures to prevent hypothermia and dehydration

SURGICAL MEASURES:

N/A

ACTIVITY:

As tolerated in hospital and on discharge

DIET:

Regular as tolerated, except when SIADH complicates course

MEDICATIONS

DRUG(S) OF CHOICE:

Empiric therapy until culture results available (need to consider local patterns of bacterial sensitivity)
  •0 to 4 weeks: ampicillin 300-400 mg/kg/d plus a third-generation cephalosporin (cefotaxime 200 mg/kg/d q4-6h OR ceftriaxone 100 mg/kg/d q12-24h); or ampicillin plus an aminoglycoside (tobramycin 7.5 mg/kg/d q6-8h prematures or infants < 1 week, 2.5 mg/kg q12h. 14-21 days treatment.
  •Age 4 to 12 weeks: ampicillin plus a third-generation cephalosporin. 10 days treatment (same doses as above).
  •Age 3 months to 18 years: third generation cephalosporin; or ampicillin plus chloramphenicol 75-100 mg/kg/d. 10 days treatment.
  •For all ages > 1 month and < 50 years - evidence is convincing that corticosteroids decrease mortality and morbidity. Dexamethasone 0.15 mg/kg q6h, started 15-20 minutes before antibiotic x 4 days. (N Engl J Med 324:1525, 1991.)
  •For all patients > 1 month with definite or probable meningitis - use vancomycin plus cefotaxime (2 gm q 4 hours) or ceftriaxone (2 gm/day)

Contraindications: Allergies to antibiotics
Precautions:
  •Ototoxicity from aminoglycoside
  •Hearing loss
  •Developmental abnormalities related to meningitis
Significant possible interactions: Refer to manufacturer's literature

ALTERNATIVE DRUGS:

  •Vancomycin
  •Antipseudomonal penicillins
  •Aztreonam
  •Quinolones (e.g., ciprofloxacin)

FOLLOW UP

PATIENT MONITORING:

Brainstem auditory evoked response (BAER) test should be done with infants prior to hospital discharge. Further followup will depend on its results and course of meningitis while in hospital.

PREVENTION/AVOIDANCE:

  •Prompt medical treatment for infections
  •Strict aseptic techniques when treating patients with head wounds or skull fractures
  •Look for evidence of CSF fistula in patients with recurrent meningitis

POSSIBLE COMPLICATIONS:

  •Seizures (20-30% during course of illness)
  •Focal neurologic deficit
  •Cranial nerve palsies (III, VI, VII, VIII) 10-20% of cases, usually disappear within a few weeks
  •Sensorineural hearing loss (10% in children)
  •Neurodevelopmental sequelae (subtle learning deficits 30%)
  •Obstructive hydrocephalus
  •Subdural effusions

EXPECTED COURSE AND PROGNOSIS:

  •Overall case fatality 14%
      •H. influenza 6%
      •Neisseria meningitidis 10.3%
      •Streptococcus pneumoniae 26.3%

MISCELLANEOUS

ASSOCIATED CONDITIONS:

Which worsen prognosis:
  •Coma
  •Seizures
  •Alcoholism
  •Old age
  •Infancy
  •Diabetes mellitus
  •Multiple myeloma
  •Head trauma

AGE-RELATED FACTORS:

Pediatric: N/A
Geriatric: Several signs and symptoms may be less evident in elderly patients with other disorders (congestive heart failure, pneumonia)
Others: Different etiologic agents, antimicrobials and dosing, and CSF findings as listed above

REFERENCES

  •Tunkel AR, Scheld WM: Issues in the management of bacterial meningitis. Am Fam Phys 1997;56(5):1355-62
  •McIntyre PB, Berkey CS, King SM, et al: Dexamethasone as adjuvant therapy in bacterial meningitis. A meta-analysis od randomized clinical trials since 1988. JAMA 1997;278(11):925-31
  •Anonymous: Therapy for children with invasive pneumococcal infections. American Academy of Pediatrics Committee on Infectious Diseases. Pediatrics;1997;99(2):289-99